Phosphatizing compositions and processes



United States Patent 3,306,785 PHOSPHATIZING COMPOSITIONS AND PROCESSES John B. Hitchcock, Wilmington, Del., assignor to E. I.

du Pont de Nemours and Company, Wilmington, Del.,

a corporation of Delaware N 0 Drawing. Filed June 4, 1963, Ser. No. 285,214 12 Claims. (Cl. 1486.15)

This invention relates to anhydrous compositions which are useful in connection with the phosphatizing of metal surfaces, and to phosphatizing processes employing such compositions.

The phosphatizing of metal surfaces is a widely practiced art. In particular, an instances where a steel or other metal article is to be painted, the adherence of the paint can 'be greatly improved by first phosphatizing the metal surface. Furthermore, the inclusion of a phosphatizing step usually produces a marked improvement in the corrosion resistance of the resulting painted metal article.

Heretofore, most phosphatizing processes have been carried out in aqueous (i.e., water-based) systems. The principal aqueous systems are those designated as iron phosphatizing, zinc phosphatizing, and manganese phosphatizing. The so-called iron phosphatizing solutions are based upon aqueous solutions of phosphoric acid. The phosphoric acid reacts with the elemental metal at the surface of the article, thereby converting said metal into an adherent phosphate-containing layer, hence the name conversion coatings. When the metal which is being treated is iron or steel, the resulting layer consists largely of iron phosphate, hence the name iron phosphatizing.

The zinc phosphatizing solutions are based upon solutions which contain not only phosphate ions but also zinc ions. Depending upon various factors, including the amount of Zinc in the solution, a relatively large portion of the resulting coating layer will consist of zinc phosphate, even when the substrate contains no zinc initially. In such a case, the zinc phosphate compound is formed at least partially by precipitation from the ingredients in the solution, rather than by reaction with metal initially located at the surface of the article.

The manganese phosphatizing systems are similar to the zinc solutions in that they contain the metal ions, i.e., manganese ions, and phosphate ions in solution; and the resulting coating layers are formed to at least some extent -by precipitation of a manganese phosphate compound.

In the aqueous phosphatizing art, the choice as to whether one selects an iron system, or a zinc ssytem, or a manganese system depends, for the most part, upon What characteristics one desires to produce in the resulting coating layer. For example, zinc systems are employed where good corrosion resistance is desired in the final painted article; and manganese systems are often employed where a thick phosphate coating is needed in order to protect an article which is to be extruded or mechanically worked.

More recently, it has been appreciated that major commercial advantages may be realized by employing anhydrous phosphatizing systems, rather than the classical aqueous systems. The term anhydrous as used herein connotes that the composition may contain small amounts of water, but that the actual phosphatizing compositions do not contain enough water to form a separate aqueous phase.

' One of the earliest of such anhydrous systems is disclosed by Verner et al. (U.S. 2,515,934), who employed from 1% to 7% of phosphoric acid in a solvent mixture containing, for example, 50% of carbon tetrachloride plus 50% of a substance such as acetone, methyl alcohol or ice amyl acetate. Verner et al. state that zinc phosphate may be used if desired, but that in their process it is entirely unnecessary. Subsequently, major improvements in anhydrous phosphatizing systems have been made, as disclosed, for example, in U.S. 2,789,070 and British 891,390. These latter systems involve using, in a vapor degreaser type of apparatus, a composition comprising a predominant amount of trichlorethylene or perchlorethylene; plus phosphoric acid; plus a solubilizer for the phosphoric acid, such as certain acid alkyl phosphates and certain alcohol compounds.

Among the advantages oifered by these substantially anhydrous systems are: the opportunity of carrying out an overall process involving cleaning plus phosphatizing plus painting while using a smaller number of processing steps than are employed in aqueous systems, thereby economizing on investment costs and on floor space; the avoidance of any contacting of the work with water, which is a prime promoter of misting; lower operating costs; and/ or improved product quality.

Notwithstanding the foregoing advantages, there is still room for considerable improvement in the anhydrous systems. In the first place, the systems tend to corrode the apparatus. As a result, unless certain quite expensive materials are used for constructing the apparatus, the life of the apparatus is unduly shortened. Secondly, the solutions tend to degrade in use. The life of the phosphatizing baths is thus not nearly as long as might be desired. As a result, the baths must be regenerated frequently, which is costly and which involves undesirable losses of materials. Thirdly, the amount of time required to deposit a given thickness of phosphate coating is longer than desired. And fourthly, the quality of the phosphatized articles and of the painted articles derived therefrom could be improved.

Accordingly, it is a primary object of this invention to provide anhydrous phosphatizing compositions and phosphatizing processes which exhibit a markedly decreased tendency to cause corrosion of apparatus in which they are used. Another important object of the invention is to provide anhydrous phosphatizing compositions which will have markedly longer periods of usefulness prior to requiring regeneration due to degradation. A further object is to provide improved coating speeds in anhydrous phosphatizing operations. A still further object is to provide compositions and processes for producing high quality phosphatized coatings on metal surfaces. A still further object is to provide improved anhydrous compositions which are useful in connectionwith the carrying out of various metal treating processes.

These and other objects are accomplished by providing anhydrous and substantially homogeneous liquid compositions comprising as the predominant ingredient a chlorhydrocarbon solvent from the group consisting of trichlorethylene and perchlorethylene; from about 1% to about 10% by weight of an oxygen-containing solvent consisting essentially of at least one member from the group consisting of alcohol compounds containing from 3 to 8 carbon atoms inclusive and acid alkyl phosphates having at least one alkyl group containing from 3 to 8 carbon atoms inclusive; from about 0.001% to about 1% :by weight of zinc in the form of a substantially solu'bilized divalent zinc compound; and from about 0.05% to about 5% by Weight of a phosphatizing phosphate compound; the foregoing ingredients constituting at least 98% by weight of the total composition.

Preferred compositions are those comprising as the predominant ingredient trichlorethylene or perch-lorethylene; from about 1% to about 10% by Weight of an alcohol containing from 4 to 5 carbon atoms inclusive; from about 0.005% to about 0.05% by weight of zinc in the form of a zinc acid ortho phosphate compound; and from 3 about 0.2% to about 0.8% by weight of orthophosphoric acid.

Trichlorethylene and perchlorethylene are particularly well adapted for use in the anhydrous compositions of this invention because their vapors are heavy, as a result of which they can be employed in a vapor degreaser type of apparatus; because they lend themselves to effective stabilization; because they are reasonably priced and relatively non-toxic; and because their boiling points are well suited for this application. Trichlorethyle-ne is particularly suit-able where it is desired to use refluxing systerns which will apply phosphatizin-g coatings at good commercial speeds and yet avoid the necessity for using high pressure steam. Perchlorethylene is particularly useful Where it is desired to carry out extra-high-speed phosphatizing operations.

The chlorhydrocarbon solvent is the predominant ingredient in the compositions of this invention in the sense that it is always present in an amount exceeding 60% by weight of the total composition. In the preferred phosphatizing compositions, the chlorhydrocarbon solvent constitutes from 90% to 98% by weight of the total composition.

The oxygen-containing solvents which are useful in the compositions of this invention include alcohols containing from 3 to 8 carbon atoms inclusive, for example, propyl alcohol, normal butyl alcohol, secondary butyl alcohol, normal amyl alcohol, secondary amyl alcohol (2-pentanol), normal hexyl alcohol, 2-ethylhexyl alcohol, cyclohexyl alcohol, benzyl alcohol, and the like. In addition to the monohydric alcohols, it is also possible to use polyhydric alcohols, such as the butanediols and the pentanediols. Also useful as oxygen-containing solvents are the acid alkyl phosphates in which the alkyl radical contains from 3 to 8 carbon atoms inclusive. These compounds may be viewed as derivatives of phosphoric acid in which one or two of the hydrogen atoms are re placed by an alkyl group derived from one of the above alcohols. In the case of the acid dialkyl phosphates, the two alkyl groups may be the same or, if desired, they may be different.

The preferred oxygen-containing solvents are the alcohols containing from 4 to 5 carbon atoms inclusive, including normal butyl alcohol, normal amyl alcohol and secondary amyl alcohol. In addition to functioning as excellent solubilizers for the other ingredients, these particular alcohols contribute an important stabilizing effect to the overall compositions.

In the actual phosphatizing compositions, these oxygencontaining solvents are present in an amount varying from about 1% to about by weight. In commercial operations, however, the various ingredients in the overall composition are used up at differing rates. When a phosphatizing bat-h has been set up and is operating, it has been found to be highly advantageous to be able to replenish the original compositions from time to time by relatively small and frequent additions of phosphatizing phosphate compound and/or zinc compound, and then to supplement the original compositions by somewhat less frequent additions of other solutions, one of which contains from 10-40% by weight of the oxygen-containing solvent together with a predominant amount of the chlorhydrocarbon solvent. This solvent mixture which is relatively rich in the oxygen-containing ingredient is an ideal medium for adding certain materials to the baths, including some of the stabilizers.

The zinc compounds which are useful in the compositions of this invention are the divalent zinc compounds which can be solubilized to the extent of at least 0.001% (calculated as elemental zinc) based upon the weight of the total composition. Suitable zinc compounds include the various zinc phosphates, zinc chloride, zinc fluoride, zinc chlorofluoride, zinc fluorophosphate, zinc carbonate, zinc formate, zinc acetate, zinc naphthenate, zinc oleate,

zinc palmitate, zinc stearate, zinc adipate, and the like. Still other zinc compounds which may be useful include the zinc .alcoholates in which the alcoholate group correspOnds to the various alcohols mentioned hereinbefore, as well as alkyl zinc compounds, such as dimethyl zinc, diethyl zinc, di-n-butyl zinc, diisoamyl zinc, and the like.

The preferred zinc compounds are the zinc orthophosphates in which from 1 to 3 of the acidic hydrogen atoms from the original orthophosphoric acid are replaced by zinc. These compounds may be prepared advantageously by reacting zinc oxide or, if desired, metallic zinc, with the phosphoric acid. The resulting product which often contains excess free phosphoric acid, is then mixed with one or both of the solvents.

It is also possible to form the divalent zinc compounds in situ, for example, by causing metallic zinc to react with phosphoric acid in the presence of the other ingredients. This procedure is not preferred, however, because the amount of time required to react a useful concentration of divalent zinc compound is either too great under these circumstances, or else the reaction, if rapid, tends to promote degradation of the solvent and/or subsequent corrosion of the phosphatizing apparatus. The presence of any relatively large surface area of metallic zinc, such as that provided by a finely divided form of the metal, is preferably avoided during the course of the phosphatizing operation.

The upper limit on zinc concentration is determined by the solubility of the particular zinc compound in the particular formulation. If the solubility limit is significantly exceeded, this is apt to result in the formation of an excessive amount of sludge. This sludge can be troublesome because it should preferably be kept from contacting the work, and because it increases the cleanout and filtration problems. Zinc concentrations which are either equal to or close to the maximum obtainable in the particular system are usually preferred. Lesser amounts are also useful, however, and may occasionally be preferred, as where it is desired to produce coatings containing only small quantities of zinc, while at the same time realizing the other advantages associated with the use of the zinc compounds, as described more fully below. A modest amount of a sludge that contains some of the precipitated divalent zinc compound may be beneficial, in that it can provide a reservoir effect to forestall depletion of the solubilized zinc compound.

The use of properly solubilized divalent zinc compounds in the compositions of this invention leads to several quite unexpected advantages. In the first place, these zinc compounds greatly decrease the tendency of the resulting compositions to corrode the equipment in which they are customarily employed. As illustrated hereinafter in the examples, the inclusion of from 0.01% or 0.02% of zinc in the form of a solubilized divalent zinc compound can decrease the corrosiveness of otherwise identical compositions by factors of as large as ten-fold or twenty-fold, or even more. Secondly, the inclusion of these zinc compounds can extend the useful bath life of compositions of the type contemplated herein by factors of as much as three-fold or four-fold or more, thereby cutting down considerably on the number of expensive clean-out operations which are required per year. Thirdly, the presence of the zinc compounds accelerates the rate at which the phosphate coating is applied, thereby increasing the amount of metal which can be coated in a given amount of time by factors of as much as 50% or or more. Fourthly, the presence of these zinc compounds makes it possible to produce phosphatized articles which, when subsequently painted, exhibit saltspray performances which are markedly superior to those exhibited by products which have been phosphatized with non-zinc-containing, but otherwise identical, compositions.

The presence of the zinc compounds not only improves the performance of the prosphatizing compositions, but it also improves the performance of versatility of compositions consisting mainly of the chlorhydrocarbon solvent and of compositions consisting mainly of combinations of the oxygen-containing solvent with a predomlnant amount of the chlorhydrocarbon solvent. These compositions may advantageously be used, for example, as degreasing solvents in operations such as those which are carried out adjacent to a subsequent anhydrous phosphatizing operation; for formulating anhydrous chromatizing compositions; or for the formulation of anhydrous paint compositions for use in operations such as those which might be carried out subsequent to an anhydrous phosphatizing operation. The zinc-containing compositions tend to be more stable in storage and shipment, and they constitute ideal compositions for formulating the phosphatizing compositions and for supplementing the baths in continuously operated phosphatizing units.

Compositions can be prepared and packaged in containers suitable for shipping, in which the chlorhydrocarbon solvent, the necessary stabilizers, and the zinc compound (with or without the oxygen-containing solvent and/ or the phosphatizing phosphate compound) have all been mixed ahead of time at the factory in the proper manner and in the proportions set forth herein. By supplying prepackaged compositions in this way, the actual operator of the metal treating process is spared the necessity of purchasing and blending the various ingredients or at most he may need to add only one or two readily obtainable ingredients. Furthermore, this approach eliminates many of the possible opportunities for errors in carrying out the formulating work. Containers suitable for packaging and shipping these compositions include drums, cans, pails, bottles, tank cars, tank wagons and the like. The containers should be provided with means for sealing against leakage of the contents and against contamination by external materials. In one embodiment, the containers may advantageously be lined with a galvanized interior surface.

The phosphatizing ingredient may be selected from any one of the various phosphoric acids or the acid salts of such phosphates. The preferred phosphatizing ingredient is orthophosphoric acid. The amount of this phosphate compound which is present may vary from about 0.05% to about 5% by weight, depending upon the operating conditions, such as time, temperature, etc. When operating at elevated temperatures, including the reflux temperatures of the solvent compositions contemplated herein, the preferred concentration of the phosphatizing phosphate compound is between 0.2% and 0.8% of orthophosphoric acid or its equivalent, based upon the weight of the total composition.

It is to be understood that the compositions of the present invention may contain one or more compounds which are known to act as stabilizers for the chlorhydrocarbon solvent ingredient. The preferred stabilizers for the compositions of this invention include olefins, such as diisobutylene; phenolic compounds, including the alkylated phenols; organic nitro compounds, including especially the polynitro aromatic compounds; quinones,

such as p-benzoquinone, dihydroxyanthraquinone, and combinations thereof. It is also noteworthy, of course, that the zinc compounds themselves contribute importantly to the stability of the compositions of this invenion. Furthermore, there appears to be a high degree of cooperative stabilizing action between the zinc compounds on the one hand, and the aromatic nitro compounds and/ or the quinone compounds on the other hand. The presence of the zinc compounds makes it feasible to use smaller amounts of other stabilizers than would otherwise be possible. This is a distinct advantage.

Although the compositions described above are believed, for the most part, to be true solutions, it is possible that at least some of the compositions may exist in the form of colloidal dispersions which are so finely divided that they exhibit essentially the same degree of permanence and non-settling that a true solution exhibits.

The compositions of this invention may be used in connection with the phosphatizing of a wide variety of metallic surfaces, including the various irons and steels, galvanized iron, aluminum, magnesium, alloys thereof, and the like. Pre-cleaning, as by means of an anhydrous degreasing process, is usually desirable. It may also be advantageous to subject the surface of the article to brushing, sand blasting, or other physical treatment prior to application of the phosphatizing treatment.

The phosphatizing compositions of the invention may be applied by any of the known methods, including dipping, spraying and flow coating. In a preferred embodiment, the compositions are applied by a process wherein the spray pressure is held below one pound per square inch, for example, about a half a pound per square inch, and a solid spray is provided, so as to be sure to hit every portion of the metal. The application temperature may vary from room temperature or below to the refluxing temperature of the compositions or above. Elevated temperatures are preferred, with the temperature at which the particular composition boils being most preferred. In this embodiment, the compositions may advantageously be used in a degreaser type of apparatus. Heating coils near the bottom of the tank maintain a constant boilup, and the dense solvent vapors form a continuous vapor zone extending from the surface of the boiling liquid up to the level of the cooling coils near the top of the apparatus. The articles to be phosphatized are carried by means of a suitable mechanism down through the vapor zone and into the boiling phosphatizing composition and are then passed out through the vapor zone, emerging therefrom as dry, phosphatized articles.

Phosphatizing times may vary from a few seconds or less up to 5 or 10 minutes or more, with the actual phosphatizing time being determined by factors such as the operating temperature, the substance being phosphatized, the weight or thickness of coating which is desired, the concentration of phosphate ingredient and the concentration of zinc ingredient. Shorter phosphatizing times are favored, within limits, by higher temperature, higher phosphate contents and higher zinc contents. When using the preferred trichlorethylene-containing compositions at their reflux temperatures, phosphatizing times generally vary from about 30 seconds to 3 minutes. Phosphatizing times of less than 2 seconds have been achieved when using the preferred perchlorethylene-based compositions at their reflux temperatures for phosphatizing galvanized iron strip. Adding ferrous phosphate, steel wool, or the like, to the baths initially can be advantageous in cases where the baths exhibit a break-in period.

Coating weights can be varied widely, with the choice depending largely upon the use to which the phosphatized article will eventually be put. The coating weight is determined by measuring the weight of material which is dissolved away after contact for 1-0 minutes at C. with an aqueous solution containing 25% by weight of chromic acid. Coating weights generally run from about 50 milligrams of coating per square foot up to about 1000 milligrams per square foot. When it is desired to maximize the corrosion resistance of the subsequently painted article, the coating weight usually varies from about 200-400 milligrams per square foot. When the coating is intended for lubrication of the metal article during a subsequent metal working operation, coating weights of 500-1000 milligrams per. square foot are generally employed. The amount of zinc which is incorporated into the final phosphate coatings depends, of course, on the amount of zinc which is present in the phosphatizing composition. By and large, however, the coatings produced from the compositions of the present invention contain markedly lower percentages of zinc than do the coatings produced from the standard aqueous zinc phos- 7 phatizing compositions. In many instances, for example, they contain only about one-fifth as much zinc. Furthermore, the coatings initially produced by this process of this invention are usually water-soluble to the extent of 50% or more of their weight, in contrast with the coatings produced in the aqueous art, which, due to the very nature of the process, are essentially water-insoluble. The phosphatized articles derived from the present compositions perform, on the average, at least as well as do the aqueous zinc phosphatized articles, and, in some situations, they perform markedly better.

The articles which have been phosphatized in accordance with the present invention may advantageously be subjected to various post-treatments, including baking at elevated temperatures, exposure to infra-red heat, treatment with dry steam, chromatizing and, of course, painting. A wide variety of paints may be employed, including in particular those in which the thinner is trichlorethylene or perchlorethylene. The phosphatized articles exhibit superior corrosion resistance, both in themselves and when painted. Paint adhesion is greatly improved and the impact resistance of the resulting painted article may likewise be improved.

Various embodiments of the invention are illustrated by the following examples. Unless otherwise stated, the percentages are based upon the total weight of the composition, and the zinc is provided by means of the reaction product of zinc oxide with 85% phosphoric acid in the ratio of 6 grams of zinc oxide per 100 ml. of acid.

Example I The first portion of this example shows the corrosiveness of an anhydrous phosphatizing solution which contains no zinc compound, while the second portion shows the decrease in corrosiveness which can be achieved by the use of the zinc-containing composition.

A bath was made up to contain about 94.2% of a technical grade of trichlorethylene, which in turn contained as stabilizers diisobutylene and p-tertiary amylphenol. The bath also contained of normal amyl alcohol, 0.5 of orthophosphoric acid, and 0.25% of dinitrotoluene. This composition was placed in a large beaker, the beaker was provided with a cover, and a loop of #316 stainless steel cooling coil was passed down through this cover so that it would be exposed to vapors in the top one-third portion of the beaker. Iron powder, in the amount of 1.5 grams, was added, and the composition was heated to refluxing temperature and maintained at that temperature for a total of 176 hours. Each day, an additional 1.5 grams of iron powder was added to maintain the exposure. Each day there were also added 0.02% of dinitrotoluene and 0.01% of p-benzoquinone, based upon the weight of the contents of the beaker, together with sufiicient amounts of a mixture of trichlorethylene and amyl alcohol to maintain the original volume and concentration. At the end oi this period, the weight of the steel coil was compared to its weight initially. Based upon these data, the corrosion rate was calculated in terms of mils per year of #316 stainless steel which would be corroded away from the cooling coils under these circumstances. The average corrosion rate in duplicate runs was 170 mils per year. Because of the extremely large surface which is introduced by means of the iron powder, this is a very extreme and accelerated test, with the results tending to be about to times as drastic as those encountered under actual commercial conditions.

A second run was made under identical conditions, except that the composition contained 0.014% by weight of zinc (calculated as elemental zinc), which was introduced into the composition by means of a solution containing 6 grams of zinc oxide in 100 milliliters of 85% phosphoric acid. When this composition was subjected to refluxing under the above-described conditions, the corrosion rate for the #316 stainless steel averaged 10 mils per year in duplicate runs. This constitutes about a 17-fold decrease in the corrosion rate of the stainless steel coils.

8 Example II This example is representative of conditions often encountered in commercial installations, and shows the decrease in corrosiveness of compositions containing two different concentrations of zinc compound, as compared to a similar composition containing no zinc.

Three separate beakers were set up, similar to the beakers employed in Example I. In addition to the cooling coils, stainless steel condensate troughs and stainless steel drip shields were included inside the beakers. These drip shields were located underneath the cooling coils, in positions characteristic of where they would appear in a Commercial phosphatizing unit. In commercial units, all three of these parts are exposed to severe corrosion conditions, with the drip shields perhaps representing the most severe conditions. Each of these three beakers was charged with a composition containing about 94.4% of technical grade trichloroethylene, 5% of normal amyl alcohol, 0.5% of phosphoric acid, 0.125% of dinitrotoluene and 0.02% of para-benzoquinone. Steel panels were introduced into the beakers at 24-hour intervals to represent a rate of work load which would be comparable to that encountered in commercial operations. The level of the solutions in the beakers was maintained by daily additions of a solution containing trichlorethylene, normal amyl alcohol, phosphoric acid and para-benzoquinone in amounts required in order to preserve the original concentrations. The contents of the beakers were refluxed for 628 hours, and the corrosion rate on the drip shields was determined after the baths had phosphatized the equivalent of 500 square feet of surface per gallon of bath. The first beaker container no zinc compound. The second beaker contained 0.01% of zinc, which was introduced initially and via the maintenance solutions in the form of a solution of zinc oxide and phosphoric acid. The third beaker contained 0.02% of zinc, introduced in the same manner. The corrosion rates on the #316 stainless steel drip shields were 12.4 mils per year with no zinc, 3.5 mils per year with 0.01% of zinc, and 1.3 mils per year with 0.02% of zinc. The inclusion of the zinc compound thus produces about a 3- to l0-fold decrease in the corrosiveness of the phosphatizing compositions. This is an important improvement from the commercial viewpoint, because a corrosion rate of 10 mils per year is about the maximum which can be tolerated, and even with the use of this high quality stainless steel, the nonzinc-containing compositions exceed the maximum allowable corrosion rate. Furthermore, even a two-fold decrease in the corrosion rate can mean a doubling of the effective life of the phosphatizing equipment, which is a major economic consideration from the viewpoint of the users of the phosphatizing compositions.

Example III This example is intended to show the markedly improved bath life which can be obtained when using the zinc-containing compositions of this invention.

A bath was made up containing the same ingredients provided in the first portion of Example I, i.e., it contained no zinc compound. This bath was operated at the refluxing temperature, and iron powder was introduced into the bath until it had been used for phosphatizing the equivalent of square feet of metal surface per gallon of bath. The bath level was maintained by periodically adding a composition which contained about 97.6% of technical grade trichlorethylene, 2% of normal amyl alcohol, 0.2% of dinitrotoluene, 0.1% of parabenzoquinone and 0.1% of phosphoric acid. In addition, extra phosphoric acid was periodically added, in order to keep the coating weights up to the desired level. During the life of the bath, it gradually become less active, and it became necessary to increase the phosphoric acid content to about 0.7% in order to maintain coating weights even as high as 197 milligrams per square foot. Panels which were phosphatized after this bath had already been used to phosphatize the equivalent of 170 square feet of surface per gallon were painted with a Dulux beige enamel paint (#752-66295) and were baked at 300 F. for 30 minutes. When these painted panels were subsequently subjectedto a standard salt spray test, they lasted for only 72 hours.

A comparative run was made except that the bath contained 0.025% of zinc. After this zinc-containing bath had been used for phosphatizing the equivalent of 383 square feet of steel surface per gallon of bath, the steel panels which were phosphatized at that stage had a desirable coating weight of 249 milligrams per square foot and these panels, when painted in the same manner described above, had a life of 648 hours in the salt spray test. This Zinc-containing bath showed no decline in phosphatizing activity whatsoever at this stage in its life and was, in fact, giving desirable coating weights at phosphoric acid contents of only 0.3% in the 90-second coating period. Similar zinc-containing compositions have shown no loss of bath life after coating the equivalent of 500 square feet or more per gallon of bath, whereas the comparable non-zinc-containing baths and other anhydrous phosphatizing baths appear to have completely lost their usefulness after they had phosphatized the equivalent of not more than 200 square feet of steel surface per gallon of bath.

Example IV This example shows the decreasing activity of baths containing no zinc compound, as compared with the prolonged period of high activity obtained when the zinc compound is present.

A series of runs was made in which steel panels were phosphatized with compositions containing about 94.4% of trichlorethylene, of normal amyl alcohol, 0.12% of dinitrotoluene, 0.02% of para-benzoquinone and phosphoric acid. Steel panels were dipped in the various phosphatizing baths for 90 seconds and the phosphoric acid content was varied in order to achieve a coating weight in the range of 250-300 milligrams per square foot. The first run contained no Zinc, the second run contained 0.01% of zinc, and the third run contained 0.02% of zinc. The initial phosphoric acid content on each run was 0.45%. Toward the end of the runs, when the equivalent of 400 square feet of steel surface had been treated per gallon of bath, it was necessary to increase the phosphoric acid content of the first run to 0.65%, and the quality of the phosphatizing coatings was decreasing. In the second run, it was only necessary to raise the phosphoric acid content to 0.5%, and the coating quality was still good. In the third run, containing 0.02% zinc, no change was made whatsoever in the composition of the bath, and it was still functioning just as effectively as it had functioned at the very outset.

Example V 1.5 grams of mossy zinc was dissolved in 1 gallon of a composition containing 94.5% of trichlorethylene, 5% of normal amyl alcohol, and 0.5% of phosphoric acid. The resulting composition contained 0.025% by weight of zinc. When used for phosphatizing at the reflux temperature, this composition produced coating weights of 210 milligrams per square foot in 75 seconds, whereas the composition prior to the inclusion of the zinc required 90 seconds to produce a coating weight of only 200 milligrams per square foot. Furthermore, the quality of the paneling which was phosphatized with the zinc-containing composition was superior, as evidenced by the fact that, when painted as described above with the Dulux beige enamel, it withstood 550 hours in the salt spray test, as compared to 432 hours for the non-zinc-containing panel.

Example VI A phosphatizing solution was prepared by dissolving zinc phosphate (Zn; (PO -4H O) in the same trichlorethylene-based composition described in the previous example. The zinc phosphate was added in an amount such as to yield a final composition containing 0.06% of zinc. The resulting composition produced a good quality of coating on steel, the weight of the coating being 488 milligrams per square foot.

Example VII This example is designed to show the improved coating speeds which are obtained when employing the zinc compositions and the improved quality of the resulting phosphatized articles.

A composition was prepared from technical-grade trichlorethylene, 5% of normal amyl alcohol, 0.4% of phosphoric acid and 0.4% of dinitrotoluene. When steel panels were dipped for seconds in this composition at its refluxing temperature, a coating weight of 222 milligrams per square foot was produced. This panel was then sprayed with a l-mil coating of Dulux Primer 764-10236 Hi-Bake White paint and baked for 18 minutes at 325 F., followed by a 2-mil coating of Dulux Topcoat 752T-33077 Baking Enamel-White, and baked for 18 minutes at 325 F. This painted panel exhibited a salt-spray life of 360 hours.

Using the identical procedure except that the phosphatizing composition contained 0.015% of zinc, a coating weight of 410 milligrams per square foot was realized and the salt-spray life was 1200 hours. The inclusion of the zinc thus nearly doubles the coating rate, while at the same time producing a marked improvement in the quality of the resulting product.

Example VIII If the coating weight is maintained constant, the inclusion of zinc in the above amount makes it'possible to use either about 25% less of free phosphoric acid or else to shorten the coating time by about 40 or 50%. Using the non-zinc-containing composition of the previous example, and painting the resulting phosphatized panel with Wyandotte #7212 black trichlorethylene-thinned paint, the salt-spray life of the resulting panel was 216 hours. A composition containing 25% less phosphoric acid (i.e., 0.3% instead of 0.4%) and also containing 0.01% of zinc produced a comparable coating weight, and the saltspray life of the panel painted with the same Wyandotte paint was 384 hours.

Example IX A composition was prepared containing about 94.2% of technical-grade trichlorethylene, 4.7% of normal amyl alcohol, 0.3% of dinitrotoluene, 0.74% of phosphoric acid and 0.025% of zinc. Steel slugs measuring 1.63 inches in diameter and 3.5 inches in length were dipped in this composition at refluxing temperature for 180 seconds. The resulting coating weights were in the range of 600-700 milligrams per square foot. The resulting slugs met all specifications for lubricant-type phosphate coatings in subsequent extrusion tests. They were able to withstand the so-called ram operation without losing corrosion resistance.

Example X A composition was prepared containing about 94.5 of perchlorethylene, ,5% of normal amyl alcohol, 0.5 of phosphoric acid and 0.02% of zinc. This composition was heated to a temperature somewhat below its refluxing temperature, and galvanized iron strip at a temperamm of about 250260 C. was introduced into the hot composition. Under these conditions, excellent quality phosphatized coatings were applied, as judged by a subsequent painting and salt spray test, using contact times of about 2 seconds, and sometimes as little as 1 second.

Example XI A composition was prepared containing about 94.6% by weight of trichlorethylene, 4.2% of amyl alcohol, 0.4% of phosphoric acid and 0.8% zinc chloride (i.e.,

about 0.4%, calculated as elemental zinc). This composition was used at the reflux temperature to coat aluminum panels, employing contact times of 30 seconds. These panels were coated with beige enamel paint, heated under a hot lamp for 30 minutes at 110 C., and placed in a water bath at 38 C. for 15 hours. As compared to panels produced in exactly the same fashion except that the zinc chloride was omitted, the resulting painted panels were in very good condition and exhibited markedly less blistering of the beige enamel paint.

Example XII A composition was prepared which was identical to that in Example XI, except that it contained 0.8% of zinc acetate (Zn(C H O -2H O), (i.e., about 0.24%, calculated as elemental zinc). Aluminum panels are coated, painted and tested according to the procedure of Example XI, except that the coating time was 90 seconds instead of thirty seconds. The resulting painted panels were of good quality.

Example XIII A composition was prepared similar to that of Example XI, except that it contained 0.6% of zinc chlorofiuoride (i.e., about 0.33%, calculated as elemental zinc). This composition, when employed at the reflux temperature, produced good quality coatings on aluminum strip.

Example XIV A composition was prepared similar to that of Example XI, except that it contained 1% by weight of zinc palmitate (i.e., about 0.11%, calculated as elemental zinc). This composition produced good quality coatings on steel panels.

Example XV A composition was prepared containing about 97.4% of trichlorethylene, 2.5% of normal butyl alcohol and 0.1% of di-n-butyl zinc. This composition was employed in a small-scale degreaser unit which was equipped to separate out and make available for measurement the amount of HCl formed as a result of the degrading of the trichlorethylene during normal usage. Over a period of a week, this zinc-containing composition produced only about one-fifth as much free hydrogen chloride as was produced by a straight trichlorethylene composition.

Example XVI A continuous run was made in which the bath composition was maintained at about 94.3% of technical grade trichlorethylene, 5% of normal amyl alcohol, 0.4% of phosphoric acid, 0.24% of dinitrotoluene, 0.02% of parabenzoquinone and 0.02% of zinc. This bath was operated continuously for the phosphatizing of metal parts for oflice furniture. The composition was supplemented periodically by using several formulations, one of which contained 75.9% of technical-grade trichlorethylene, 21% of normal amyl alcohol, 2% of dinitrotoluene, 1% of phosphoric acid and 0.0275 of zinc, and small amounts of the two stabilizers. The bath operated satisfactorily in this fashion over a period of several months.

I claim:

1. An anhydrous and substantially homogeneous liquid composition comprising as the predominant ingredient a chlorhydrocarbon solvent from the group consisting of trichlorethylene and perchlorethylene; from about 1% to about by weight of an oxygen-containing solvent consisting essentially of at least one member from the group consisting of alcohol compounds containing from 3 to 8 carbon atoms inclusive and acid alkyl phosphates having at least one alkyl group containing from 3 to 8 carbon atoms inclusive; from about 0.001% to about 1% by Weight of zinc in the form of a substantially solubilized divalent Zinc compound; and from about 0.05% to about 5% by weight of a phosphatizing phosphate compound; the foregoing ingredients constituting at least 98% by weight of the total composition.

2. An anhydrous and substantially homogeneous liquid composition comprising as the predominant ingredient trichlorethylene; from about 1% to about 10% by weight of an alcohol containing from 3 to 8 carbon atoms inclusive; from about 0.001% to about 1% by weight of zinc in the form of a substantially solubilized divalent zinc compound; and from about 0.05% to about 5% by weight of phosphoric acid; the foregoing ingredients constituting at least 98% by weight of the total composition.

3. An anhydrous and substantially homogeneous liquid composition comprising as the predominant ingredient perchlorethylene; from about 1% to about 10% by weight of an alcohol containing from 3 to 8 carbon atoms inclusive; from about 0.001% to about 1% by weight of zinc in the form of a substantially solubilized divalent zinc compound; and from about 0.05% to about 5% by weight of phosphoric acid; the foregoing ingredients constituting at least 98% by weight of the total composition.

4. An anhydrous and substantially homogeneous liquid composition comprising as the predominant ingredient a chlorhydrocarbon solvent from the group consisting of trichlorethylene and perchlorethylene; from about 1% to about 10% by weight of an alcohol containing from 4 to 5 carbon atoms inclusive; from about 0.001% to about 1% by weight of zinc in the form of a substantially solubilized divalent Zinc compound; and from about 0.05 to about 5% by weight of a phosphatizing phosphate compound; the foregoing ingredients constituting at least 98% by weight of the total composition.

5. An anhydrous and substantially homogeneous liquid composition comprising as the predominant ingredient a chlorhydrocarbon solvent from the group consisting of trichlorethylene and perchlorethylene; from about 1% to about 10% by weight of an alcohol containing from 3 to 8 carbon atoms inclusive; from about 0.001% to about 1% by weight of zinc in the form of a zinc phosphate compound; and from about 0.05% to about 5% by weight of a phosphatizing phosphate compound; the foregoing ingredients constituting at least 98% by weight of the total composition.

6. A substantially anhydrous and substantially homogeneous liquid composition comprising as the predominant ingredient a chlorhydrocarbon solvent from the group consisting of trichlorethylene and perchlorethylene; from about 1% to about 10% by weight of an alcohol containing from 4 to 5 carbon atoms inclusive; from about 0.005% to about 0.05% by weight of zinc in the form of a Zinc acid orthophosphate compound; and from about 0.2% to about 0.8% by weight of orthophosphoric acid; the foregoing ingredients constituting at least 98% by weight of the total composition.

7. A composition according to claim 1 in which the phosphatizing phosphate compound is orthophosphoric acid which is present in an amount between 0.2% and 0.8% by weight.

8. A composition according to claim 1 to which there has been added up to 1% by weight of nitro aromatic compound as a stabilizer for the chlorhydrocarbon solvent.

9. A composition according to claim 1 to which there has been added up to 5% of a quinone compound as a stabilizer for the chlorhydrocarbon solvent.

10. A process for phosphatizing a phosphatizable metal surface which comprises contacting said surface with a composition according to claim 1.

11. A process for phosphatizing a steel surface which comprises contacting said surface with a composition according to claim 1 in which the phosphatizing phosphate compound is orthophosphoric acid which is present in an amount between 0.2% and 0.8% by weight, the process being carried out substantially at the refluxing temperature of the composition.

12. A method of carrying out a continuous process for phosphatizing metal surfaces which comprises maintaining substantially at its refluxing temperature a composition comprising as its predominant ingredient a chlorhydro- 13 carbon solvent from the group consisting of trichlorethylene and perchlorethylene, from about 1% to about 10% by weight of an alcohol containing from 4 to 5 carbon atoms inclusive, from about 0.005% to about 0.05% by weight of zinc in the form of a Zinc acid orthophosphate compound, and from 0.2% to 0.8% by weight of orthophosphoric acid, the foregoing ingredients constituting at least 98% by weight of the total composition; maintaining the proportions of zinc and orthophosphoric acid within the above-specified ranges by periodically adding a zinc phosphate compound and orthophosphoric acid; and maintaining the volume of the composition by periodically adding a solvent mixture, said mixture comprising at least 60% by weight of the said chlorhydrocarbon solvent and from 10% to 40% by weight of the said alcohol.

References Cited by the Examiner ALFRED L. LEAVITT, Primary Examiner.

RALPH S. KENDALL, Examiner. 

1. AN ANHYDROUS AND SUBSTANTIALLY HOMOGENOUS LIQUID COMPOSITION COMPRISING AS THE PREDOMINANT INGREDIENT A CHLORHYDROCARBON SOLVENT FROM THE GROUP CONSISTING OF TRICHLORETHYLENE AND PERCHLORETHYLENE; FROM ABOUT 1% TO ABOUT 10% BY WEIGHT OF AN OXYGEN-CONTAINING SOLVENT CONSISTING ESSENTIALLY OF AT LEAST ONE MEMBER FROM THE GROUP CONSISTING OF ALCOHOL COMPOUNDS CONTAINING FROM 3 TO 8 CARBON ATOMS INCLUSIVE AND ACID ALKYL PHOSPHATES HAVING AT LEAST ONE ALKYL GROUP CONTAINING FROM 3 TO 8 CARBON ATOMS INCLUSIVE; FROM ABOUT 0.001% TO ABOUT 1% BY WEIGHT OF ZINC IN THE FORM OF A SUBSTANTIALLY SOLUBILIZED DIVALENT ZINC COMPOUND; AND FROM ABOUT 0.05% TO ABOUT 5% BY WEIGHT OF A PHOSPHATIZING PHOSPHATE COMPOUND; THE FOREGOING INGREDIENT CONSTITUTING AT LEAST 98% BY WEIGHT OF THE TOTAL COMPOSITION. 